1. Field of the Invention
The present invention relates to a control device of an internal combustion engine.
2. Description of the Related Art
As a control device for an internal combustion engine, one has been known which judges a required torque based on an accelerator opening degree etc. and controls operation of a fuel injector or an opening degree of a throttle valve so as to realized this required torque. In general, in such a control device of an internal combustion engine, first a target fuel injection amount and target cylinder air filling amount (or target value of equivalent value of cylinder air filling amount (that is, for example, cylinder intake air flow rate or cylinder air filling rate)) are set based on the required torque, then the operation of the fuel injector and the opening degree of the throttle valve are controlled so that the actual fuel injection amount and cylinder air filling amount (or its equivalent value) matches the target fuel injection amount and target cylinder air filling amount (or target value of equivalent value of cylinder air filling amount).
The cylinder air filling amount (or its equivalent value) is more specifically adjusted by controlling the opening degree of the throttle valve (hereinafter referred to as the “throttle opening degree”) to a target opening degree set in accordance with the target cylinder air filling amount (or target value of equivalent value of cylinder air filling amount), but even if making the throttle opening degree the target opening degree, a certain time is required until the actual cylinder air filling amount (or its equivalent value) becomes the target cylinder air filling amount (or target value of equivalent value of the cylinder air filling amount). That is, a change of the cylinder air filling amount (or its equivalent value) occurs with a delay from the change of the throttle opening degree.
Such a delay affects the control of the internal combustion engine, so obtaining a grasp of the extent of the delay is important. As an indicator showing the extent of this delay, the response time constant (63% response time) τ of the cylinder air filling amount (or its equivalent value) is known. Such a response time constant τ has previously been found using a map (for example, see Japanese Unexamined Patent Publication (Kokai) No. 2002-332884).
However, to actually prepare a map of the above response time constant τ, a tremendous amount of time is required. That is, to prepare a map, it is necessary to find the response time constant τ by successively changing arguments such as the engine speed, the operating timings of the intake and exhaust valves, etc. This work is tremendous. Further, due to the increase in the number of maps and arguments required, map search operations increase and the control load ends up increasing.